Echo ranging systems



United States 2,901,726 Patented Aug. 25, 1959 ECHO RANGING SYSTEMSRobert A. Fryklund, Dedham, Mass, assignor to Raytheon Company, acorporation of Delaware Application December 19, 1952, Serial No.326,906

7 Claims. (Cl. 340-3) This invention relates to electron dischargesystems and more particularly to systems used for echo ranging purposes,such as sonic depth sounders.

In the field of sonic depth sounders it is well known that a pulse ofenergy may be transmitted from a vessel through the water to a remoteobject, such as the bottom of the water body or another object moving inthe water body, and a reflected echo may be received from the remoteobject. The reflected echo may be then used in a time measuring systemwhich indicates the elapsed time between the initiation of transmissionof the energy pulse through the water and the received echo; this, inturn, indicating the distance to the remote object. Among the well-knowntypes of indicators are the rotating disk carrying a red light and therecording type indicator wherein a stylus produces a mark onelectrically sensitive paper. The use of either of these indicatingdevices has previously required an impedance transformer to produce thenecessary voltages to operate the indicators. Furthermore, attempts tooperate both types of indicators in parallel from a transformer outputwere unsatisfactory,

since the impedance of the light loaded the output of the transformer toa point where the stylus would not produce clear marks on the sensitivepaper.

This invention discloses that a cathode follower may be used to feedeither of the aforementioned indicators thereby producing an extremelysimple output coupling system which eliminates the need for atransformer. In addition, both indicators may be operated in parallelwith indications appearing on both indicators.

This invention further discloses that a grid-leak detector may be usedto drive the cathode follower with the anode of the grid-leak detectorbeing connected directly to the grid of the cathode follower, therebyeliminating the conventional coupling condenser and grid load resistorwhich would otherwise be required.

Other and further objects and advantages of the invention will becomeapparent as the description thereof progresses, reference being had tothe accompanying drawing wherein the single figure illustratesdiagrammatically one embodiment of the invention.

Referring now to the drawing, there is shown a transducer 10 whichperiodically emits a pulse of high intensity directional sonic energy inresponse to an impulse from a driver 11, which is connected thereto. Thereturning echoes from the remote object, such as the bottom 12, arepicked up by the transducer 10 and are fed through an amplifier 13, theoutput of which is shown here by the way of example, as thepotentiometer 14. The variable tap of potentiometer 14 is connectedthrough a coupling condenser 16 to the grid 17 of a grid-leak detectorcomprising one half 18 of a duo-triode. Grid 17 is also connected toground through a grid load resistor 19. The cathode 20 of triode 18 isconnected to ground. The plate 21 of triode 18 is connected to B+through a plate load resistor 22 and to the grid 23 of the other half18a of the duo-triode. The cathode 24 of triode 18a is connected toground through a cathode load resistor 25,

which may be bypassed, if desired, by a bypass condenser 26. The plate27 of triode 18a is connected to B+ through a plate current limitingresistor 28. The values of condenser 16 and resistor 19 are adjusted tohave a long time constant with respect to a period of oscillation of thetransducer 10, but are short with respect to the repetition rate of thekeyer 11. As a result, the returned echoes applied to the triode half 18through the amplifier 13 and condenser 16 are rectified by gridrectification due to the drawing of grid current by the grid 17 and aresubstantially filtered by the filtering action of condenser 16 andresistor 19 according to well-known grid-leak detecting practice. Therectified signal appears at the plate 21 across the plate load 22, wherethe high frequency peaks may be bypassed to ground according to standardgrid-leak detector practice by a condenser (not shown), and is directlycoupled to the grid 23 of the cathode follower triode section 18a.

The output of the cathode follower is connected to a recording indicatorgenerally indicated at 29, which may be, for example, of the typedisclosed in my copending application, Serial No. 119,905, filed October6, 1949, now Patent No. 2,715,055. Briefly, such an indicator has ametal backing member 30 which is grounded and across which the recordpaper 31 is drawn. The output of cathode follower 18a is fed to a stylus32, carried by an endless conductive belt 33 riding on pulleys 34 drivenby a synchronous motor 35, by means of a brush 36 contacting one of thepulleys 34.

The motion of the stylus 32 across the paper 31 is synchronized with theoperation of the switch 37, which is periodically closed when the stylus32 is substantially at the top of the paper 31. Closure of switch 37keys the driver 11, thereby producing an output pulse which energizesthe transducer producing the transmitted pulse of sonic energy. Thereturning echoes appearing as impulses at the cathode 24 of the cathodefollower are fed to the stylus 32, thereby producing markings as at 38under the stylus 32 thus indicating the distance traveled by the sonicenergy.

The chassis of the recording depth sounder indicated at 39 acts asground, and hence as the return path for the signals of the variouscircuits.

The output of the cathode follower may also be fed, for example, by line40 to a remote indicator, which may be, for example, of the rotating redlight type disclosed in my copending application, Serial No. 220,684,filed April 12, 1951, now Patent No. 2,845,513, line 40 being connectedthrough a slip ring 41 to one side of a neon lamp 42, which is rotatedin a circle illustrated diagrammatically at 43 by a synchronous motor44, which is synchronized with the synchronous motor 35 in the recordingdepth sounder. The other side of the neon lamp 42 is connected through asecond slip ring 45 to ground. The chassis 46 of the remote indicatormay also serve as ground for the circuits of that system. Thus it may beseen that, by the use of a cathode follower type of output, one of thesliding electrical contacts in the red light indicating system may be atground potential, thereby minimizing the insulation requirements of thedevice.

This completes the description of the particular embodiment of theinvention illustrated herein. However, many modifications thereof willbe apparent to persons skilled in the art without departing from thespirit and scope of this invention. For example, the sensitivitypotentiometer 14 may be placed in the grid circuit of the amplifier 13rather than the output circuit thereof; the limiting resistor 28 in theplate circuit of the cathode follower may be made adjustable to adjustthe limit of the current therethrough and, hence, the limiting of theoutput signal excursion or, if desired, the resistor 28 may beeliminated altogether and the anode 27 may be connected directly to 3.B+. In addition, the condenser 26. may be eliminated if desired.Accordingly, it is desired that this invention be not limited to theparticular details of the embodiment illustrated and described hereinexcept asdefined bythe appended claims.

What is claimed is:

1. An electron discharge system comprising a souroe of signals, a gridleak detector, a cathode follower directa ly coupled to said detector,and a recording indicator and flashing light indicator both coupleddirectly to the cat11-v ode. electrode at the output of said cathodefollower.

2. An electron discharge system comprising a grid leak detector, a D.C.amplifier having a D.C. bias applied thereto by connection of the inputelectrode of said amplifier through a D.C. path to the output electrodeof said detector to provide. a predetermined D.C. voltage level at theoutput electrode of said amplifier, a voltagesensitive indicatorconnected through a D. -C. path directly to said output electrode ofsaid amplifier, said indicator being energizable at a D.C. level greaterthan. said predetermined D.-C. level, a source of signals connected tothe input electrode of said detector whereby said signals are rectifiedand amplified by said detector, said amplifier being responsive to theoutput of said detector for generating output signals to change saidpredetermined D.C, level and, thereby, to energize said indicator.

3. An electron discharge system comprising a detector including elementsconnected between the grid and ground for accomplishing grid-leakdetection, an amplifier have ing a D.C. bias applied thereto byconnection of the input of said amplifier through a D.C. path to theoutput of said detector to provide a predetermined D.Q. voltage level atthe cathode of said amplifier, an indicator directly connected to thecathode of said amplifier, and a source of signals connected betweensaid grid and groundof said detector whereby said signals are rectifiedand amplified by said detector, said amplifier being responsive to theoutput of said detector for generating signals to change said D. -C.voltage level and, thereby, to energize said indicator.

4. An electron discharge system comprising a detector including elementsconnected between the grid and ground for accomplishing grid-leakdetection, an amplifier having a bias voltage applied thereto byconnection of the input of said amplifier through a D.C. path to theoutput of said detector, said biasvoltage having amagnitude dependentupon the zero-signal operating point of said detector, an indicatordirectly connected to the oathode of said amplifier and having appliedthereto a D.C. volt age dependent on said bias voltage, and a source ofsignals connected between said grid and ground of said detector wherebysaid signals are rectified and amplified by said detector, saidamplifier being responsive to the output of said detector for generatingsignals to change said D.C. voltage and, thereby, to energize saidindicator.

5. An electron discharge system comprising a detector including in agrid to ground input circuit a capacitor and an impedance foraccomplishing grid-leak detection, an amplifier'having a bias voltageapplied thereto by connection of the input of said amplifier through aD.C. path to the output of said detector, said bias voltage having a mnit d depende t n the z s s ial o eratin point of said detector, aplurality of voltage-sensitive indicators directly connected to thecathode of said amplifier and having applied thereto a predeterminedD.C. voltage dependent on said bias voltage, and a source of signalsconnected to said input circuit for generating output signals for saidamplifier of suflieient amplitude to change the D.C. voltage at saidcathode for energization of said indicators.

6. An electron discharge system comprising a source of pulse signalshaving a predetermined time interval be tween pulses, a detector, anetwork connected to the input of said detector for accomplishing gridleak detection, said network being responsive to said pulse signals andhaving a time constant substantially less than the time interval betweensaid pulse signals, a cathode follower directly coupled through a D.C.path to said detector, and a eco d ng indicator d ashin l ht ndis t b pldire ly h h a Pat t the cathod ectrode at the output of said cathodefollower.

A p l -ech system comp in a scars? of P91 signals, an echo receiverincluding a detector having a lt r n w r wh s t me s an s s bst nt aless the time interval between said pulse signals for detec ing chsignals d i f m i P 1 si nals a D.C. amp i r having a -C- a l ed heretoby on e on f e pu of id amp ifie throu h a 1-0- p th to h o tpu of s ide e t to P o de a pts e r mined l e level t output o sa d lifier, and avoltage ens tive indi ato o ne ted throu h a p h d e y to said u put oai ampl fierisait indicator be g energizable at a D.C. level greaterthan said predetermined D.C. level, said echo signals being fed t t einput f sa d e ct whe eb sa d i als. a rectified by said detector, andsaid amplifier being respon? sive to the, output of said detector forgenerating output signals to ch nge said predetermined D.C, level and,thereby, to energize said indicator.

References Cited in the file of this patent UNITED STATES PATENTS,

2,157,856 Koch May 9, 1939 2,465,990 Anderson Apr. 5, 1949 2,466,711Kenyon Apr. 12 1949 2,467,202 Gardiner Apr. 12, 1949 2,502,938 FryklundApr. 4, 1950 2,509,208 Busignies et a1 May 30, 1950 2,510,687 De VoreJune 6, 1950 2,538,487 Volkers Jan. 16, 1951 2,538,488 Volkers Jan. 16,1951 2,710,787 Witt June 14, 1955 2,714,136 Greenwood Aug. 2, 19552,736,774 Robinson Feb. 28, 1956 2,788,509 Bolzmann Apr. 9, 1957 OTHERREFERENCES Gray: Applied Electronics (2nd ed.), 1943, John Wiley & Sons,Inc., p. 715.

Landee: Electronic Designers Handbook, .McGraw-Hill Book Co., Inc.,1957, pp. 7-93.

Seeley: Electron Tube Circuits, p. 343, 1950.

